Problem: What do the following two equations represent? $-4x+5y = 5$ $20x-25y = -25$
Solution: Putting the first equation in $y = mx + b$ form gives: $-4x+5y = 5$ $5y = 4x+5$ $y = \dfrac{4}{5}x + 1$ Putting the second equation in $y = mx + b$ form gives: $20x-25y = -25$ $-25y = -20x-25$ $y = \dfrac{4}{5}x + 1$ The above equations turn into the same equation, so they represent equal lines.